Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

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LONG-TERM DEBT - SCHEDULE (Details) - USD ($) $ in Millions	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
LONG-TERM DEBT
Long-term debt, gross	$ 10,407		$ 9,907
Unamortized discount, net	(36)		(32)
Debt issuance costs	(54)		(47)
Current maturities	(116)		(500)
Total	$ 10,201		9,328
9.25% senior debentures due 2019
LONG-TERM DEBT
Debt instrument interest rate stated percentage	9.25%
Long-term debt, gross	$ 116		116
4.10% senior notes due 2021
LONG-TERM DEBT
Debt instrument interest rate stated percentage	4.10%
Long-term debt, gross	$ 1,249		1,249
3.125% senior notes due 2022
LONG-TERM DEBT
Debt instrument interest rate stated percentage	3.125%
Long-term debt, gross	$ 813		813
2.60% senior notes due 2022
LONG-TERM DEBT
Debt instrument interest rate stated percentage	2.60%
Long-term debt, gross	$ 400		400
2.70% senior notes due 2023
LONG-TERM DEBT
Debt instrument interest rate stated percentage	2.70%
Long-term debt, gross	$ 1,191		1,191
8.75% medium-term notes due 2023
LONG-TERM DEBT
Debt instrument interest rate stated percentage	8.75%
Long-term debt, gross	$ 22		22
3.50% senior notes due 2025
LONG-TERM DEBT
Debt instrument interest rate stated percentage	3.50%
Long-term debt, gross	$ 750		750
3.40% senior notes due 2026
LONG-TERM DEBT
Debt instrument interest rate stated percentage	3.40%
Long-term debt, gross	$ 1,150		1,150
3.00% senior notes due 2027
LONG-TERM DEBT
Debt instrument interest rate stated percentage	3.00%
Long-term debt, gross	$ 750		750
7.20% senior debentures due 2028
LONG-TERM DEBT
Debt instrument interest rate stated percentage	7.20%
Long-term debt, gross	$ 82		82
8.45% senior debentures due 2029
LONG-TERM DEBT
Debt instrument interest rate stated percentage	8.45%
Long-term debt, gross	$ 116		116
4.625% senior notes due 2045
LONG-TERM DEBT
Debt instrument interest rate stated percentage	4.625%
Long-term debt, gross	$ 750		750
4.40% senior notes due 2046
LONG-TERM DEBT
Debt instrument interest rate stated percentage	4.40%
Long-term debt, gross	$ 1,200		1,200
4.10% senior notes due 2047
LONG-TERM DEBT
Debt instrument interest rate stated percentage	4.10%
Long-term debt, gross	$ 750		750
4.20% senior notes due 2048
LONG-TERM DEBT
Debt instrument interest rate stated percentage	4.20%
Long-term debt, gross	$ 1,000		0
1.50% senior notes due 2018
LONG-TERM DEBT
Debt instrument interest rate stated percentage	1.50%	1.50%
Long-term debt, gross	$ 0		$ 500
Variable rate bonds due 2030
LONG-TERM DEBT
Variable interest rate	1.90%		1.80%
Long-term debt, gross	$ 68		$ 68